The presence of solitary dark neurons in material fixed by perfusion was noted when white matter as compared with gray matter was poorly fixed, as may happen when (a) amounts of perfusates are small, approximately 1-2% of body weight, (b) the fixative is introduced 5 minutes or longer after interruption of the systemic circulation, or (c) the brain is removed after postmortem intervals shorter than 4 hours when Bouin's solution is used. The histochemical demonstration of glycogen was intensified after utilization of a perfusion procedure in which various recommendations were incorporated.